Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$66.84	10.445%	$73.8214	$73.82	$73.80	$73.80
Purchase #2	$166.78	8.291%	$180.6077	$180.61	$180.60	$180.60
Purchase #3	$35.42	4.288%	$36.9388	$36.94	$36.95	$36.90
Purchase #4	$34.41	4.348%	$35.9061	$35.91	$35.90	$35.90
Purchase #5	$148.67	12.338%	$167.0129	$167.01	$167.00	$167.00
Purchase #6	$128.57	11.138%	$142.8901	$142.89	$142.90	$142.90
Purchase #7	$112.87	4.696%	$118.1704	$118.17	$118.15	$118.20
7 purchase totals =	$693.56		$755.3474	$755.35	$755.30	$755.30